Abstract: Multiple microwave oscillators can be phase locked such that the power output of multiple oscillators can be coherently combined to achieve a single output which has the total sum power of the multiple oscillators. Multiple oscillators assembled in a power combining array are phase locked using a locking signal provided at each oscillator via strategic placement of a partial obstruction between combined multiple oscillators and a load. This locking signal includes a minimum threshold level and preselected phase. A method for phase locking multiple microwave oscillators includes steps of combining power output of multiple microwave oscillators to achieve a single output to a load and inserting a partial obstruction between said at least two multiple oscillators and said load. The partial obstruction configured to provide a combined microwave oscillator signal including a minimum threshold and preselected phase.